<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <h1>ddd</h1>

    <script>


        let user = {
            info: {
                name: "why",
                age: 10,
                height:1.9
            }
        }

        let height = user.infos?.height ?? 20
        console.log(height);


    </script>
</body>
</html>